One-step surfactant-free controllable synthesis and tunable up-conversion/down-shifting white light emissions of Sr2YF7 crystals doped with Ln3+ ions†
In this work, uniform and monodisperse Sr2YF7 spheres were successfully synthesized via a facile one-step hydrothermal route without employing any surfactant. Particularly, a well-defined morphology of Sr2YF7 crystals ranging from spherical to octahedral shape was first achieved by adjusting the pH values. In addition, the spherical products doped with 6% Ln3+ (Ln = La, Ce, Pr, Sm, Gd, and Dy) show different sizes ranging from 300 to 600 nm. The Sr2YF7 crystals also exhibit excellent multicolor DS/UC luminescence properties after doping with different Ln3+ ions. Energy transfer from Tb3+ to Eu3+ was observed in Sr2YF7 crystals; the Sr2YF7:Dy3+ crystals showed nearly white light emission under UV excitation; Sr2YF7:Yb3+/Er3+/Tm3+ crystals could produce pure white light with a CIE color coordinate of (0.3123, 0.3005) by controlling the doping concentrations of Er3+ and Tm3+ ions under 980 nm excitation. The as-prepared phosphors may potentially serve as light, color displays and markers in biological imaging.